1. Technical Field
The present invention belongs to the technical field of semiconductor devices, and especially relates to a structure for interconnecting copper with a medium of low dielectric constant and the integration method thereof.
2. Description of the Related Art
With the continuous development of large-scale integrated circuit technology, the feature size of semiconductor devices is reducing constantly and the chip area is increasing gradually. As a result, people are facing the problem of how to address the significant increase of RC (R and C refer to resistance and capacity respectively) delay caused by the rapid increase of wire length. Especially as the influence of the capacity between metal wiring becomes more and more significant and further causes apparent decrease of device performance, it has become a critical factor restricting the further development of the semiconductor industry. Many measures have been taken to reduce the RC delay caused by interconnection.
The distribution capacity and interconnection resistance between interconnections lead to signal transmission delay. Since copper features low resistance, excellent anti-electromigration properties and high reliability, the study on changing routine aluminum interconnections to copper interconnection with low resistance has been carried out so as to decrease the metal interconnection resistance and further to reduce the interconnection delay effect. Decrease of capacity between interconnections can also reduce relay. As the distribution capacity C is directly proportional to the relative dielectric constant K of circuit layer insulation dielectrics, using materials with low K value (K<3) to replace the traditional SiO2 dielectric as the insulator of different circuit layers has become the requirement for high speed chip development. Since the relative dielectric constant of air is 1, it is an ideal insulation medium. Therefore, the air gap between metals can reduce interconnection RC delay effectively.